Marty Liquori, in his 1982 book Real Running, discusses both warming up and stretching. He says that stretching is "overrated, period," except in the case of an injury area. This was at least a view held by many elite distance runners at the time of the book's publication. But Liquori does stress the importance of warming up before a run. Even an elite runner might take 12 minutes to complete the first mile, and Liquori urges lesser runners to follow suit. For reference, Liquori once held the American record in the mile with a time 3:51.
When you first start running, especially in the morning, your tendon-muscle complexes will be relatively short. This makes them prone to tearing and other damage. By easing into a run slowly, you give your body a chance to literally morph into a form which can better handle the abuse you are about to give it.
Believe it or not, you actually warm up faster when it's cold outside, because your body increases blood flow to your internal areas, at the cost of cold hands and feet.
As a semi-competitive triathlete myself, and former long distance runner, when I go on a run I usually do some light stretching after warming up, if for no other reason than it feels good.